The human nose acts as a means of actively heating and humidifying the breathing air under physiological conditions. However, the artificial respiration of patients requires that the nose be bypassed and the breathing air is sent directly into the human trachea with a tube (flexible tube). The inspired air must therefore be humidified and optionally also heated to physiological values in order to maintain the lung function in case of artificial respiration.
Prior-art respiration humidifiers have a humidifying chamber as a cavity with an inlet opening and with an outlet opening for the breathing air. Water to be evaporated is located at the bottom of the humidifying chamber. The vapor cannot disadvantageously be taken up completely by the breathing air because of the limited contact surface between the water and the air, on the one hand, and the high velocity of flow of the breathing air or the short residence time of the breathing air in the humidifying chamber, on the other hand, so that sufficient humidifying effect is not guaranteed. Furthermore, the necessary homogeneous mixing of the air and vapor is not possible in a satisfactory manner. In addition, the water may form a spray upon impact of the air jet from the inlet opening.
To reduce these drawbacks, provisions have already been made to insert in the humidifying chamber a guide body, which channels the flow of the breathing air in the humidifying chamber. The breathing air is guided here such that a direct impingement of the breathing air on the water is avoided and the breathing air is guided along a wall enclosing the humidifying chamber towards the water surface in order to obtain the necessary contact between the breathing air and the surface of the water. The relatively small cross-sectional areas of the breathing air channels formed by the guide body in the humidifying chamber lead to high flow velocities and hence to very short residence times, so that the uptake of vapor by the breathing air at the water surface is very limited.
To avoid splash water in the pipelines connected to the inlet opening and to the outlet opening, it is known that baffle plates can be arranged as a shielding against the splashing of water. These baffle plates cause a disadvantageous additional flow resistance for the breathing air and require an additional design effort and manufacturing cost.
U.S. Pat. No. 4,225,542 shows a class-forming respiration humidifier. The respiration humidifier has a ring-shaped cross section. The outer limitation of the humidifying chamber is formed by a water-absorbing material. The water present in the bottom of the humidifying chamber is in contact with the water-absorbing material, so that the water can rise up in the water-absorbing material. A tube, through which the breathing air to be humidified is introduced into the lower area of the humidifying chamber, is arranged concentrically in the interior of the humidifying chamber. The humidified air flows out again at the upper end of the humidifying chamber, so that the direction of flow of the breathing air in the humidifying chamber extends vertically from bottom to top.
Furthermore, a respiration humidifier of this class with a humidifying chamber of a rectangular cross section is known from U.S. Pat. No. 3,954,920. Water is present in the bottom of the humidifying chamber. The cover wall of the humidifying chamber has an inlet opening and an outlet opening for letting the breathing air in and out. Water-absorbing material is directed vertically in the humidifying chamber and dips into the water in the lower area, so that it can be taken up by the water-absorbing material for evaporation.
The vertical orientation of the water-absorbing material in the humidifying chamber in the upper area of the absorbing material disadvantageously brings about a low degree of saturation with water in both class-forming documents because the path over which the water must rise in this area is long. The absorbing material therefore has a high evaporation capacity in the lower area close to the water only. Furthermore, there is no protection against splashing of water caused by the breathing air flowing in, because only a small percentage of the surface of the water is covered by the absorbing material. The geometry of the absorbing material causes an unfavorable air flow, which fails to guarantee a reliable homogeneous mixing of the air and vapor.